1. Field of the Invention
The invention relates to a process for producing molten pig iron or molten steel pre-products from charging substances formed of iron ores and fluxes and at least partially comprising fines, wherein the charging substances are directly reduced to sponge iron in at least one reduction zone by the fluidized layer method, the sponge iron is melted in a melting-gasifying zone under supply of carbon carders and oxygen-containing gas, and a CO and H.sub.2 -containing reducing gas is produced, which is injected into the reduction zone, is reacted there, is withdrawn as an export gas and is supplied to a consumer, as well as a plant for carrying out the process.
2. Description of the Related Prior Art
A process of this kind is known, for instance, from Austrian Patent AT-B 390 622. According to AT-B 390 622, charging substances having largely varying grain sizes are processed, the charging substances being pre-reduced and separated by wind screening into fractions of different grain sizes, which are then completely reduced separately. However, this known one-step process only offers a low thermal utilization of the reducing gas and consequently involves an elevated consumption of reducing gas. Nor is the optimum utilization of the energy chemically bound in the reducing gas feasible.
According to Austrian Patent AT-B 387 403, siderite-containing and/or hydrated charging substances are calcined in a fixed-bed heating zone preceding the fixed-bed direct reduction zone, wherein, however, only coarse lumps of iron-ore-containing charging substances capable of being processed merely in the fixed bed are used for charging.
From U.S. Pat. No. 5,082,251, a direct reduction process is known, according to which fine ores rich in iron are reduced after complex ore preparation, such as drying, screening and breaking, in a system of whirl layer reactors in cascade arrangements by aid of reformed natural gas or oil so as to obtain a very narrow grain size distribution. Subsequently, the iron powder is hot- or cold-briquetted. Smoke gas is used as the fluidizing gas in the preheating stage, which is produced by burning air and natural gas; thus, external energy must be introduced, only the sensible heat of the whirling gases being utilizable. In contrast, reduction according to the process of the present invention is effected by means of solid carbon carriers, such as coal, and hence, according to the invention, CO reduction is preponderant, whereas, according to U.S. Pat. No. 5,082,251, the direct reduction of ore primarily is effected by H.sub.2.